i see your in iowa. Call Bruce at advance transmission in knoxville. He deals with powerglides and racing transmisison from every weekend brackets to extremely high hp cars. Hes had trannys in cars up to 3000 hp. He is currently working with transmission specialties getting their new input shafts and output shafts for powerglides to make them live in the high hp applications. Everything he sells he has tested in his own cars included a 57 chevy pro mod/nitro coupe car as well a supercharged blown hemi Spitzer top dragster. Most company's will tell you a transmission will hold certain applications and most of the time they are over estimating. Bruce knows what stuff will hold and live for a long time. Last i knew, he had a trans live 6 or 7 full seasons without freshening. he said the only reason it had problems was they changed engines that up'd the hp and over did the trans.
All his transmission have a full race season warranty and he will stand behind anything he sells. Also he out racing just like any other guy so at track support is always a plus!
heres a link to his sight.
www.advancetransmission.net
or call him at 641-828-7030